This invention relates in general to methods of manufacturing splined members, such as are commonly used in the driveshaft assemblies. In particular, this invention relates to an improved method of manufacturing a splined member for use in such a driveshaft assembly.
Drive train systems are widely used for generating power from a source and for transferring such power from the source to a driven mechanism. Frequently, the source generates rotational power, and such rotational power is transferred from the source to a rotatably driven mechanism. For example, in most land vehicles in use today, an engine/transmission assembly generates rotational power, and such rotational power is transferred from an output shaft of the engine/transmission assembly through a driveshaft assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical driveshaft assembly includes a hollow cylindrical driveshaft tube having a pair of end fittings, such as a pair of tube yokes, secured to the front and rear ends thereof. The front end fitting forms a portion of a front universal joint that connects the output shaft of the engine/transmission assembly to the front end of the driveshaft tube. Similarly, the rear end fitting forms a portion of a rear universal joint that connects the rear end of the driveshaft tube to the input shaft of the axle assembly. The front and rear universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts.
Not only must a typical drive train system accommodate a limited amount of angular misalignment between the source of rotational power and the rotatably driven device, but it must also typically accommodate a limited amount of relative axial movement therebetween. For example, in most vehicles, a small amount of relative axial movement frequently occurs between the engine/transmission assembly and the axle assembly when the suspension of the vehicle articulates during normal operation, such as when the vehicle is driven over a bumpy road. To address this, it is known to provide a slip joint in the driveshaft assembly. A typical slip joint includes first and second members that have respective structures formed thereon that cooperate with one another for concurrent rotational movement, while permitting a limited amount of axial movement to occur therebetween.
One type of slip joint commonly used in conventional driveshaft assemblies is a sliding spline type slip joint. A typical sliding spline type of slip joint includes male and female members having respective pluralities of splines formed thereon. The male member is generally cylindrical in shape and has a plurality of outwardly extending splines formed on the outer surface thereof. The male member may be formed integrally with or secured to an end of the driveshaft assembly described above. The female member, on the other hand, is generally hollow and cylindrical in shape and has a plurality of inwardly extending splines formed on the inner surface thereof. The female member may be formed integrally with or secured to a yoke that forms a portion of one of the universal joints described above. To assemble the slip joint, the male member is inserted within the female member such that the outwardly extending splines of the male member cooperate with the inwardly extending splines of the female member. As a result, the male and female members are connected together for concurrent rotational movement. However, the outwardly extending splines of the male member can slide relative to the inwardly extending splines of the female member to allow a limited amount of relative axial movement to occur between the engine/transmission assembly and the axle assembly of the drive train system.
In the past, the male and female splined members have usually been formed from steel, and the splines of such members have been manufactured by machining portions of such members so as to provide the desired splines. Although this method has been effective, the use of the machining process to form the splines has resulted in the generation of waste material, which is inefficient. Also, the use of the conventional machining process to form the splines can generate dimensional variances that result from normal manufacturing tolerances and practices. More recently, the male and female splined members have usually been formed from aluminum alloys having relatively low elongation factors, such as 6061-T6 aluminum. The use of these aluminum alloys has been found to be desirable because aluminum is much lighter in weight than steel. However, the use of the machining process to form the splines in the aluminum members still results in the generation of waste material and dimensional inaccuracies. Thus, it would be desirable to provide an improved method of manufacturing a splined member, such as for use in a vehicular driveshaft assembly, that avoids the generation of waste material and minimizes the amount of dimensional inaccuracies.